The present invention relates to a battery comprising a cathode, an anode and an electrolyte in which the anode includes an anode mixture layer including a tin-containing alloy powder.
A large number of small-sized portable electronic devices such as camera/VTR (video tape recorder) combination systems, cellular phones, laptop computers or the like have come into widespread in accordance with recent advances in electronics, and a development for reducing their sizes and weights has proceeded. Accordingly, a development in compact and lightweight batteries having a high energy density, specifically secondary batteries as portable power sources used in the portable electronic devices has proceeded. As such secondary batteries, for example, batteries which use a graphite material using intercalation reaction of lithium ions into graphite layers, or a carbon material using an application of insertion/extraction reaction of lithium ions into/from pores as an anode material have been developed and have been in practical use.
However, in accordance with a recent increase in performance of portable devices, a demand for capacity has been growing, so the batteries are required to have a characteristic in which no decline in capacity occurs in spite of repeated cycles of charge and discharge, that is, an excellent charge-discharge cycle characteristic. Moreover, in accordance with diversification of use conditions of the devices, a demand for batteries exhibiting an excellent capacity at high load has been growing. As a method of obtaining such characteristics, for example, it can be considered that light metal such as lithium metal or the like is used as-is as an anode material. However, in this case, in a charging process, the light metal in dendrite form is likely to be deposited on an anode, and a current density becomes extremely high at a tip of a dendrite, so the charge-discharge cycle characteristic may decline due to the decomposition of an electrolyte or the like, or when the dendrite excessively grows to reach a cathode, an internal short circuit may be induced.
In order to inhibit the deposition of lithium in dendrite form, it is considered that a specific alloy is used as an anode active material, and during charge, lithium deposited on a surface of the anode is alloyed with a base metal of an alloy of the anode active material to be introduced into the alloy. As such an alloy, a lithium-lead (Pb) alloy (for example, refer to Japanese Examined Patent Application Publication No. Hei 3-53743, Hei 5-34787, Hei 7-73044 and Hei 8-138654) or a bismuth (Bi)-tin (Sn)-lead-cadmium (Cd) alloy (for example, refer to Japanese Examined Patent Application Publication No. Hei 4-47431 and Hei 3-64987) have been disclosed. However, lead, bismuth and cadmium are not preferable in the viewpoint of recent environmental protection.
Moreover, although a method using a silicon (Si) alloy which causes very little damage to the environment has been proposed (refer to Japanese Unexamined Patent Application Publication No. Hei 7-302588, Hei 10-199524, Hei 7-326342, Hei 10-255768 and Hei 10-302770), the reaction between the silicon alloy and an organic solvent is so large that the charge-discharge cycle characteristic is poor, so it could not be put to practical use.
Further, a method using tin or a tin-containing alloy has been proposed. As the tin-containing alloy, for example, alloy materials of tin and nickel (Ni) (refer to Japanese Examined Patent Application Publication No. Hei 4-12586, Japanese Unexamined Patent Application Publication No. Hei 10-162823 and Sho 10-308207), alloy materials of lithium, aluminum (Al) and tin (refer to Japanese Unexamined Patent Application Publication No. Sho 61-66369), alloy materials of tin and zinc (Zn) (refer to Japanese Unexamined Patent Application Publication No. Sho 62-145650), materials of a tin alloy containing 1 wt % to 55 wt % of phosphorus (P) (refer to Japanese Unexamined Patent Application Publication No. Hei 8-273602), Cu2NiSn and Mg2Sn (refer to Japanese Unexamined Patent Application Publication No. Hei 10-223221), alloy materials of tin and copper (Cu) (refer to Japanese Unexamined Patent Application Publication No. Sho 10-308207), materials of a mixture of a tin-containing phase which absorbs lithium, and a phase made of manganese (Mn), iron (Fe), cobalt (Co), nickel and copper which does not absorb lithium (refer to Japanese Unexamined Patent Application Publication No. Hei 11-86854) have been disclosed.
However, in the case of a battery using tin or a tin-containing alloy, such a problem that the battery cannot fully satisfy requirements for the capacity, the charge-discharge cycle characteristic and a load characteristic arises.
Moreover, in accordance with diversification of use conditions of the devices, a demand for batteries exhibiting an excellent charge-discharge cycle characteristic under high temperature conditions has been growing. However, such a problem that the conventional batteries cannot obtain sufficient characteristics also arises.
In view of the foregoing, it is an object of the invention to provide a battery capable of obtaining a superior battery capacity and a superior charge-discharge cycle characteristic under high temperature conditions, and improving the load characteristic.